A variety of research reports have suggested that schizophrenic performance deficits may be mediated by disturbances in the processing of proprioceptive information or in the integration of proprioceptively mediated information with that derived from other sensory modalities. A recent investigation in our laboratory has revealed the existence of a performance deficit involving the maintenance of induced muscle tension which successfully discriminated unmedicated psychiatric patients from controls at moderate tension levels and, schizophrenics from affectives at high tension levels (Appendix). The specific aims of the proposed investigations are to determine the mechanisms underlying this deficit as they relate to basic sensory-motor integrative processes as well as to higher level cognitive/attentional processes. Subjects are tested in a dual-task paradigm that permits independent parametric manipulations of sensory, motor, and attentional variables. The results of these proposed studies should produce a clearer understanding of the role of sensory-motor information processing in schizophrenic and affective patients. In addition, with further investigations of pharmacological and biochemical variables, relations between task performance and biochemical metabolite levels may permit both better diagnostic precision in the form of marker variables and may provide better predictors for responsivity to pharmacological interventions.